Free Tool
Welcome to our Body Fat Calculator — a tool for understanding your body composition beyond what the scale shows. Body fat percentage gives a clearer picture of your fitness than weight alone, helping you set realistic goals and track real progress. Choose a method below based on what you have available — a tape measure is all you need for the U.S. Navy Method, while the Jackson-Pollock and Durnin-Womersley methods require skinfold calipers and are best suited for trainers or those with access to proper equipment.
Each method estimates body fat percentage a different way — choose the one that matches the equipment you have available.
Inputs: gender, height (in), neck circumference (in), waist circumference (in), hip circumference (in — females only).
Men
%BF = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women
%BF = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Uses simple tape-measure circumferences — no special equipment required. Validated against underwater weighing (Hodgdon & Beckett, 1984).
Inputs: gender, age, skinfolds in mm — men: chest, abdomen, thigh; women: tricep, suprailiac, thigh.
Body Density (men)
1.10938 − (0.0008267 × sum) + (0.0000016 × sum²) − (0.0002574 × age)
Body Density (women)
1.0994921 − (0.0009929 × sum) + (0.0000023 × sum²) − (0.0001392 × age)
%BF (Siri equation)
(495 / Body Density) − 450
Requires skinfold calipers and proper technique — best suited for trainers or those experienced with caliper measurements.
Inputs: gender, age, skinfolds in mm — same 7 sites for both genders: chest, midaxillary, tricep, subscapular, abdomen, suprailiac, thigh.
Body Density (men)
1.112 − (0.00043499 × sum) + (0.00000055 × sum²) − (0.00028826 × age)
Body Density (women)
1.097 − (0.00046971 × sum) + (0.00000056 × sum²) − (0.00012828 × age)
%BF (Siri equation)
(495 / Body Density) − 450
The most detailed skinfold method — requires calipers and a partner to measure most sites accurately.
Inputs: gender, age, skinfolds in mm — same 4 sites for both genders: tricep, bicep, subscapular, suprailiac.
Step 1
L = log10(sum of the 4 skinfolds)
Step 2
Body Density = C − (M × L), using the age/gender table below
Step 3 — %BF (Siri equation)
(495 / Body Density) − 450
| Age Band | Male C | Male M | Female C | Female M |
|---|---|---|---|---|
| <17 | 1.1533 | 0.0643 | 1.1369 | 0.0598 |
| 17–19 | 1.1620 | 0.0630 | 1.1549 | 0.0678 |
| 20–29 | 1.1631 | 0.0632 | 1.1599 | 0.0717 |
| 30–39 | 1.1422 | 0.0544 | 1.1423 | 0.0632 |
| 40–49 | 1.1620 | 0.0700 | 1.1333 | 0.0612 |
| 50+ | 1.1715 | 0.0779 | 1.1339 | 0.0645 |
An alternative method using age-adjusted calculations, validated across ages 16-72 (Durnin & Womersley, 1974).
Want a fuller picture? Try our BMI Calculator for a quick weight-to-height check, our Calorie Calculator to estimate your daily energy needs, or our One-Rep Max Calculator to track your strength training progress.
